Orthotics
A prescription foot orthosis is an in-shoe brace which is designed to correct
for abnormal foot and lower extremity function [the lower extremity includes the
foot, ankle, leg, knee, thigh and hip]. In correcting abnormal foot and lower
extremity function, the prescription foot orthosis reduces the strain on
injured structures in the foot and lower extremity, allowing them to heal and
become non-painful. In addition, prescription foot orthoses help prevent
future problems from occurring in the foot and lower extremity by reducing
abnormal or pathological forces acting on the foot and lower extremity. A
prescription foot orthosis is more commonly known by the public as a "foot
orthotic".
Podiatrists prescribe two main types of prescription foot orthoses for their
patients, accommodative orthoses and functional foot orthoses. Both types of
prescription foot orthoses are used to correct the foot plant of the patient so
that the pain in their foot or lower extremity will improve so that normal
activities can be resumed without pain. However, accommodative and functional
foot orthoses are generally made using different materials and may not look or
feel the same. Both types of prescription foot orthoses are nearly always
prescribed as a pair to allow more normal function of both feet [similar to
having both the left and right wheels of a car realigned in a front end
alignment].
Accommodative Foot Orthoses
Accommodative foot orthoses are used to cushion, pad or relieve pressure from a
painful or injured area on the bottom of the foot. They may also be designed to
try to control abnormal function of the foot. Accommodative orthoses may be made
of a wide range of materials such as cork, leather, plastic foams, and rubber
materials. They are generally more flexible and soft than functional foot
orthoses. Accommodative orthoses are fabricated from a three dimensional model
of the foot which may be made by taking a plaster mold of the foot, stepping
into a box of compressible foam, or scanning the foot with a mechanical or
optical scanner.
Accommodative orthoses are useful in the treatment of painful callouses on the
bottom of the foot, diabetic foot ulcerations, sore bones on the bottom of the
foot and other types of foot pathology. The advantages of accommodative orthoses
are that they are relatively soft and forgiving and are generally easy to adjust
in shape after they are dispensed to the patient to improve comfort. The
disadvantages of accommodative orthoses are that they are relatively bulky, have
relatively poor durability, and often need frequent adjustments to allow them to
continue working properly.
Functional Foot Orthoses
Functional foot orthoses are used to correct abnormal foot function and, in so
doing, also correct for abnormal lower extremity function. Some types of
functional foot orthoses may also be designed to accommodate painful areas on
the bottoms of the foot, just like accommodative foot orthoses. Functional foot
orthoses may be made of flexible, semi-rigid or rigid plastic or graphite
materials. They are relatively thin and easily fit into most types of shoes.
They are fabricated from a three dimensional model of the foot which may be made
by taking a plaster mold of the foot, stepping into a box of compressible foam,
or scanning the foot with a mechanical or optical scanner.
Functional foot orthoses are useful in the treatment of a very wide range of
painful conditions of the foot and lower extremities. Big toe joint and lesser
toe joint pain, arch and instep pain, ankle pain and heel pain are commonly
treated with functional foot orthoses. Since abnormal foot function causes
abnormal leg, knee and hip function, then functional foot orthoses are commonly
also used to treat painful tendinitis and bursitis conditions in the ankle, knee
and hip, in addition to shin splints in the legs. The advantages of functional
foot orthoses are that they are relatively durable, infrequently require
adjustments and more likely to fit into standard shoes. The disadvantages are
that they are relatively difficult to adjust and relatively firm and less
cushiony.
Foot and Lower Extremity Biomechanics
The study of the mechanical nature of the foot and lower extremity is called
biomechanics. It is a specialized branch of science that uses the mechanical
principles of physics to study the motions and forces on the human body.
Podiatrists receive specialized, in-depth training during their four years of
medical training on how the movements and forces in the foot affect the
movements and forces in the rest of the lower extremity, and how the movements
and forces in the lower extremity affect the movements and forces in the foot.
No other medical specialty has this in-depth training, which is necessary to
understand lower extremity pathology as it relates to the biomechanics of foot
function. Therefore, the podiatrist is the most qualified medical specialist to
diagnose and treat foot pathology.
Understanding the biomechanics of the foot and lower extremity is of critical
importance when the mechanism of an injury must be determined to decide on a
appropriate treatment plan for the patient. In addition, biomechanics plays an
important part in the planning for corrective surgery for injuries, such as
tendon ruptures or bone fractures, or for the surgical correction of deformities
of the foot, such as hammertoes, bunions, or heel spurs. As a result of the
podiatrist's training and expertise in biomechanics, they will often prescribe
either functional or accommodative orthoses as part of their treatment plan. In
many instances, an orthosis will be all that is required for the successful
treatment of foot or lower extremity pathology. In most instances, however, an
orthosis will be prescribed along with other therapies, such as stretching or
strengthening exercises, oral or injectable medications, and specific types of
shoes, in order to insure the fastest healing for the patient.
The Process of Prescribing Foot Orthoses
In order to design and fabricate a prescription foot orthosis, the podiatrist
must perform a biomechanical examination of the foot and lower extremities.
Angular measurements are taken of the toes, foot, ankle, knees and hip to
determine the amount and level of any structural or functional deformities. This
examination is done while the patient is on an examining table and also while
standing. The podiatrist will also do a walking and/or running gait analysis of
the patient to determine how their foot and lower extremity functions during
these activities. Abnormalities from the biomechanical examination and gait
examination are noted in the patient's chart for future consideration in the
design and fabrication of the prescription foot orthosis.
The podiatrist then next must make a three dimensional model of the patient's
feet in order to make a prescription foot orthosis. This is done by either
applying plaster splints to the patient's foot, by having the patient step into
a box of compressible foam, or having the foot scanned by a mechanical or
optical scanner. The resultant three-dimensional model of the foot is then used
along with a detailed orthosis prescription from the podiatrist to have the
prescription foot orthoses made for the patient. Most podiatrists have a
specialty podiatric orthosis laboratory make their orthoses while some
podiatrists make their own prescription foot orthoses.
Advantages and Disadvantages of Prescription Foot Orthoses
The advantages of prescription foot orthoses are many. First of all, they are
custom made for each foot of each patient, so that each foot orthosis will only
fit one foot correctly. In addition, since they fit so exactly to the persons
foot, they can be made with relatively rigid, durable materials with a minimal
chance of discomfort or irritation to the patients foot. Prescription foot
orthoses also have a much greater potential to effectively and permanently treat
painful conditions, all the way from the toes to the lower back, since they are
designed specifically for an individual's biomechanical nature.
For example, in children, prescription foot orthoses are used to prevent
abnormal development of the foot due to flatfoot or intoeing or outtoeing
disorders. In athletes, prescription foot orthoses are used to allow the athlete
to continue training and competing without pain. And in most adult patients,
prescription foot orthoses are used to allow more normal daily activities
without pain or disability.
One disadvantage to prescription foot orthoses is that they are relatively
expensive when compared to store bought over-the-counter foot inserts. Even
though the over-the-counter inserts do help some people with mild symptoms, they
do not have the potential to correct the wide range of symptoms that
prescription foot orthoses can since they are made to fit a person with an
"average" foot shape.
In this fashion, prescription foot orthoses may be considered to be analogous to
prescription eyeglasses. Over-the-counter eyeglasses may work for some people
since they are made to correct for the average eye. However, over-the-counter
eyeglasses will almost never work as well as prescription eyeglasses.
Prescription foot orthoses, since they are custom made to each foot of a
patient, are almost always more corrective and comfortable than over-the-counter
foot inserts, even though over-the-counter inserts do work for some people.
